In a transition nozzle combustion system (also known as a tangential combustor), the combustion system may be integrated with the first stage of the turbine. Specifically, the geometric configuration of the combustor may include a liner and a transition piece arranged to replace the functionality of the first stage nozzle vanes. The configuration thus may be used to accelerate and turn the flow of hot combustion gases from a longitudinal direction from the combustor to a circumferential direction for efficient use in the turbine. The efficiency of a transition nozzle combustion system thus generally focuses on limiting the pressure drop across the integrated liner, transition piece, and first stage nozzle vanes. Efficiency also may focus on limiting parasitic cooling and leakage flows—especially near the aft portion of the transition nozzle where the combustion gas flow may become choked. Specifically, the transition nozzle and the associated support structures may require a cooling system to withstand the aerodynamic heat loads associated with the high Mach Number combustion gas flows. Given such, a portion of the cooling flow may be used to cool the transition nozzle though film cooling. This portion of the flow, however, does not participate in charging the combustion flow and, hence, reduces overall system performance.
There is thus a desire for an improved transition nozzle combustion system. Preferable such a transition nozzle combustion system may provide adequate cooling of the components positioned about the hot combustion gas path while limiting the extent of the parasitic cooling and leakage flow loses for improved component lifetime and overall efficiency.